PORT-AU-PRINCE, HAITI - Haiti's government and its aid partners fought Friday to contain a cholera epidemic that has killed at least 140 people in the nation's worst medical emergency since the Jan. 12 earthquake.

The World Health Organization (WHO) said the virulent diarrheal disease, which has affected more than 1,500 people in central Haiti, would be the first cholera epidemic in a century in the disaster-prone and impoverished Caribbean nation.

The Red Cross and other humanitarian agencies were rushing doctors, medical supplies and clean water to Saint-Marc in the Artibonite region, the outbreak zone north of Port-au-Prince. As of Friday, no cases had been reported in the crowded capital.

One humanitarian worker who visited the main hospital in Saint-Marc called it a "horror scene."

"The courtyard was lined with patients hooked up to intravenous drips. It had just rained, and there were people lying on the ground on soggy sheets, half-soaked with feces," wrote David Darg, of the U.S.-based Operation Blessing International, in an account published on the Thomson Reuters Foundation's AlertNet Web site.

Darg said villagers in the countryside around Saint-Marc were begging for clean water.

The region, Haiti's breadbasket, had received tens of thousands of fleeing survivors from the January quake, which killed as many as 300,000 people and injured thundreds of thousands.

"It is a cholera epidemic," said Dr. Michel Thieren, of the Pan American Health Organization, the WHO's regional office. It was not possible to say whether the epidemic was at its peak, he said, but it was definitely not over.

Haitian Prime Minister Jean-Max Bellerive said the government was worried about the disease spreading to crowded quake survivors' camps in Port-au-Prince, where about 1.5 million people live, and Health Minister Alex Larsen announced an emergency prevention program.

"This disease is very dangerous. It can kill in three hours because once the diarrhea starts it doesn't stop." Larsen said.

Cholera usually comes from consuming water or food contaminated by cholera bacteria and is not likely to spread from person to person. But outbreaks could be potentially explosive among malnourished or displaced people living in unsanitary, crowded conditions, according to the WHO.